When a surface such as that of a vehicle body is being refinished, particularly after repair of accident damage, it is common practice to apply body fillers and stoppers (a very fine filler) and a series of layers of primers, stone chip or corrosion protection coatings, paint coats and sealants etc which are each rubbed down before application of the next coat in order to obtain a smooth surface and to assist in re-working of top paint coats and lacquers. Filling materials are used to repair indentations, scratches etc and these are prepared by sanding, filing and other abrasive techniques to achieve a smooth surface. This may be done using power assisted equipment or by hand. A range of abrasive materials may be used such as sand papers, production papers, wet and dry abrasive papers and sanding pads. Coarse abrasives are initially used then finer and finer abrasives until the desired finish is achieved.
To assist in this process it is known to apply a guide coat to the surface being re-finished. The guide coat is an intermediate coat applied to one of the re-finishing coats to provide a visual guide to the progress of such smoothing operations. As the surface of a coating of, say, primer is eroded by sanding, the guide coat is removed from the high spots of that coating whereas the guide coat remains on low spots or other indentations. The operator may continue the abrading process to smooth out these irregularities and thus remove the guide coat or it may prove necessary to correct surface irregularities revealed by further filling or re-working the surface (eg by panel beating) before the sanding process is continued. The guide coat thus helps the operator to achieve a smooth finish by visually enhancing any irregularities remaining in the surface during sanding and by indicating the areas which have not yet been sanded. Such a guide coat may be used at each stage of the process, ie for each coating which requires rubbing down, or as required by the operator. A guide coat may also be applied to highlight particular surface irregularities or blemishes such as scratches, pin holes, `orange peel` or dry spray edges.
The guide coat is conventionally formed by a dilute mixture of paint and thinners, eg 1 part paint to 10 parts thinners, sprayed over the surface being refinished. However, this suffers from the disadvantages that surrounding areas need to be masked, as the thinners based coating may stain or otherwise damage good paintwork, and as the thinners is usually a volatile petrochemical, such as a cellulose solvent, the operator should wear a mask and fume extraction is required for the area in which the work is carried out. With increasing legislation designed to protect the environment, severe restrictions are likely to be imposed on such fume extraction and the use of such solvent based guide coats may no longer be permitted. In addition, there are the usual problems associated with the storage of such flammable liquids.
This invention aims to provide a simple, convenient method and apparatus which enable a guide coat to be formed without the need to use such petrochemical solvents and so avoids the disadvantages of these materials.